U.S. patent application number 11/318167 was filed with the patent office on 2006-07-27 for adaptive relay management.
This patent application is currently assigned to Samsung Electronics (UK) Ltd.. Invention is credited to Byron Bakaimis.
Application Number | 20060166618 11/318167 |
Document ID | / |
Family ID | 34113198 |
Filed Date | 2006-07-27 |
United States Patent
Application |
20060166618 |
Kind Code |
A1 |
Bakaimis; Byron |
July 27, 2006 |
Adaptive relay management
Abstract
A method of controlling a plurality of relays in communication
with a base station in a cell. The controlling method comprises the
steps of evaluating usage requirements in a cell, and varying the
number and/or type of relays used in order to meet the usage
demands based on the evaluation.
Inventors: |
Bakaimis; Byron; (Staines,
GB) |
Correspondence
Address: |
DILWORTH & BARRESE, LLP
333 EARLE OVINGTON BLVD.
UNIONDALE
NY
11553
US
|
Assignee: |
Samsung Electronics (UK)
Ltd.
Chertsey
GB
|
Family ID: |
34113198 |
Appl. No.: |
11/318167 |
Filed: |
December 23, 2005 |
Current U.S.
Class: |
455/11.1 |
Current CPC
Class: |
H04B 7/155 20130101;
H04W 88/085 20130101 |
Class at
Publication: |
455/011.1 |
International
Class: |
H04B 7/15 20060101
H04B007/15 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 23, 2004 |
GB |
0428271.1 |
Claims
1. A method of controlling a plurality of relays in communication
with a base station in a cell, wherein said method comprises the
steps of evaluating usage requirements in a cell, and varying the
relays used in order to meet the usage demands based on the
evaluation.
2. A method according to claim 1, wherein the relays used are also
based on the capabilities and availability of the relays in the
cell.
3. A method according to claim 1, wherein at least some of the
relays are terrestrial based and are movable with respect to the
cell.
4. A method according to claim 1, wherein at least some of the
relays are mounted onto a vehicle.
5. A method according to claim 4, wherein the vehicle is associated
with a pre-set route and schedule.
6. A method according to claim 3, wherein at least one of the
mobile relays comprises a user terminal.
7. A method according to claim 6, wherein a plurality of
predetermined scenarios are stored by the base station, and the
most appropriate relays for each scenario are pre-selected.
8. A method according to claim 7 wherein the base station assesses
the capabilities of the relays.
9. A method according to claim 8, wherein each relay is accorded a
classification according to its capabilities.
10. A method according to claim 9, wherein, during initial
communication with a base station, each relay communicates data
indicative of its capabilities to the base station.
11. A method according to claim 7, wherein each relay assesses its
own capabilities.
12. A method according to claim 1, wherein the number of relays may
be altered based on change in any or all of usage requirements,
relay capabilities or relay availability.
13. A method according to claim 11 wherein the capabilities of each
of the relays within the cell are assessed periodically.
14. A method according to claim 13, wherein the capabilities of
each of the relays are assessed at predetermined intervals.
15. A method according to claim 13, wherein the capabilities of
each of the relays are assessed based on external triggers.
16. A method according to claim 15, wherein the external trigger is
joining or leaving of a relay.
17. A method according to claim 11, wherein the base station
broadcasts a signal on a channel receivable by each of the relays,
said signal including an evaluation of current usage
requirements.
18. A method according to claim 17, wherein the signal broadcast to
the relays defines one of a plurality of pre-defined scenarios, and
the relays store data relating to each scenario.
19. A method according to claim 18, wherein, if a relay assesses
that it is suitable for use in a network, it attempts to register
with the base station to be available for relaying future
communications.
20. A method according to claim 7, wherein the base station
broadcasts a preferred number of relays for use in a particular
scenario, and only permits that number of relays to register.
21. A method according to claim 19, wherein the network assigns
weighting factors for relay capabilities.
22. A method according to claim 19, wherein the location of the
relays in the cell is determined, and the relays' locations are a
factor in the selection of relays.
23. A method according to claim 1, further comprising a
telecommunications network.
24. A mobile telecommunications network comprising at least one
mobile relay mounted upon a terrestrial vehicle.
25. A mobile telecommunications network according to claim 24,
wherein said vehicle is a bus, coach or train.
26. A mobile telecommunications system for a telecommunication
network comprising a plurality of relays in communication with a
base station, wherein the base station is operable to adaptively
control the number of relays used in the network depending upon
current usage requirements.
Description
[0001] The present invention relates to an adaptive relay
management method and particularly an adaptive relay management
method for use with a cellular mobile telephone network.
[0002] In mobile telecommunication systems, a mobile terminal (e.g.
a mobile phone) is used to access a telecommunications network. The
network essentially comprises two main systems: a network switching
system and a base station.
[0003] The network switching system comprises a plurality of
network switching centres, which act as `gateways` that provide
interconnections to other mobile and fixed networks.
[0004] The base station is effectively divided into a plurality of
elements. Two of these elements are the base station controller and
the base transceiver station. The base station's area of
responsibility is determined by the radio coverage achieved from
the transceiver site, and this area will generally cover a large
number of mobile terminals.
[0005] The base transceiver station controls all radio functions
associated with transmission to, and reception from, mobile
terminals.
[0006] The base station controller controls the base transceiver
station. In practice the base station controller will control a
plurality of base transceiver stations.
[0007] As will be appreciated by those skilled in the art, the cost
of construction of a base transceiver station is significant. Thus,
in order to minimize cost and maximise coverage, relays are used
within the network. Relays are operable to receive and transmit
signals from a mobile terminal to the base transceiver station and
vice versa. Thus, relays allow for additional coverage from what
otherwise would be the case with just a base transceiver
station.
[0008] Relays may also be used in areas of poor coverage, or if
there is an occasional concentration of mobile terminals--for
example at a football match.
[0009] Current relays are generally fixed in areas to help overcome
shadowed areas--for example due to large buildings. Relays are also
used to extend coverage outside the range of the base transceiver
station.
[0010] In a given network, many different types of relay may be
used. Possible forms of mobile relays could comprise further mobile
phones, lap-top computers or PDAs. The use of (e.g.) mobile phones
and PDAs has advantages that these devices generally already have a
degree of in-built functionality that may be utilized in a network.
A drawback is the drain on the battery power of the mobile
device.
[0011] Alternatively, purpose built relays may be used. This
arrangement overcomes the drawback of draining battery power.
However, there are costs associated with the construction and
installation of the relay.
[0012] It would be desirable to improve current systems, and
particularly to be able to provide a more comprehensive coverage,
whilst maintaining efficient performance.
[0013] According to a first aspect of the present invention there
is provided a method of controlling a plurality of relays in
communication with a base station in a cell, wherein said method
comprises the steps of evaluating usage requirements in a cell, and
varying the relays used in order to meet the usage demands based on
the evaluation.
[0014] It is preferred that the capabilities and availability of
the relays are also used when determining which relays are to be
used to meet the usage demands in the cell.
[0015] Preferably at least some of the relays are terrestrial based
and are moveable with respect to the base station.
[0016] Preferably at least some of the relays are mounted onto a
vehicle, and preferably a vehicle associated with a pre-set route
and schedule. Buses, coaches and trains are most preferred as these
vehicles generally follow a set time-table and route, and hence
their location is generally known, or at least can be
estimated.
[0017] Preferably at least one of the mobile relays comprises a
user terminal.
[0018] It is preferred that a plurality of scenarios are
predetermined, and the most appropriate relays for each scenario
are pre-selected.
[0019] In a preferred first general embodiment, the means to assess
the capabilities of the relays is located at the base station, and
possibly at the base transceiver station. However, it is equally
preferred that the means to assess the capabilities of the relays
is located at a base station controller.
[0020] In a preferred general second embodiment it is preferred
that each individual relay assesses its own capabilities.
[0021] In the first general embodiment it is preferred that each
relay in the network is classified according to capability,
wherein, during initial communication with a base station each
relay communicates data indicative of its classification to the
base station.
[0022] It is preferred that the number of relays used in the
network may be altered based on changes to any or all of the cell
usage requirements, relay capabilities and relay availability.
[0023] Preferably the capabilities of each of the relays within the
cell are assessed periodically. It is particularly preferred that
the capabilities of each of the relays are assessed at
predetermined intervals. Alternatively, or as well as, it is
preferred that the capabilities of each of the relays are assessed
based on external triggers. Preferably the external trigger is the
joining or leaving of a relay within the cell.
[0024] In the second general embodiment it is preferred that the
base station broadcasts a signal on a channel receivable by each of
the relays, said signal including an evaluation of current usage
requirements. It is particularly preferred that the signal
broadcast to the relays defines a pre-defined scenario. Thus, each
individual relay may compare their capabilities with the evaluation
of current requirements.
[0025] It is preferred that if a relay assesses that it is suitable
for use in the network it registers with the base station. In a
particularly preferred embodiment the base station broadcasts the
preferred number of relays for use in a particular scenario, and
only permits that number of relays to register.
[0026] In a particularly preferred embodiment the network assigns
weighting factors for relay characteristics. Accordingly, when each
relay assesses their capabilities with those that are required, the
more important elements may be emphasised.
[0027] In a further preferred embodiment each relay compares its
characteristics with those required for a set of pre-determined
scenarios. Preferably a hierarchical list is made for each
scenario. This arrangement allows for the most appropriate relays
to be selected for a given scenario, and further provides details
of the next most suitable relay, should the most suitable become
unavailable. Accordingly, a set of relays from the currently active
relays in the cell is effectively pre-selected for each scenario.
However, multiple contingency plans are built into each scenario as
each relay is hierarchically listed the `next best` relay is always
known. In a preferred embodiment the location of the relays in the
cell is determined, and it is further preferred that the relays'
location is a factor in at least one of the predetermined
scenarios.
[0028] According to a second aspect of the present invention there
is provided a mobile telecommunications network operable to
function according to any aspect of the above recited method.
[0029] According to a third aspect of the present invention there
is provided a mobile telecommunications network comprising at least
one mobile relay mounted upon a terrestrial vehicle.
[0030] Preferably the transport is a bus, coach or train. However,
any form of transport, such as a car, may be used.
[0031] In order that the present invention be more readily
understood, specific embodiments thereof will now be described with
reference to the accompanying drawings.
[0032] FIG. 1 shows an example of a mobile telecommunications
network.
[0033] FIG. 2 is a table showing an example of how relays may be
identified and classified according to a first embodiment.
[0034] FIG. 3 shows an example of how the most optimum relays are
evaluated for each scenario according to a first embodiment.
[0035] FIG. 4 illustrates a base station controller signalling
function according to a first embodiment.
[0036] FIG. 5 shows a table that links characteristics of potential
relays, and is also used as a starting point of the evaluation
process (illustrated in FIG. 6).
[0037] FIG. 6 shows a realisation of an evaluation process
according to a first embodiment.
[0038] FIG. 7 shows a relay evaluation method according to a second
embodiment.
[0039] FIG. 8 shows a table illustrating a first method of
evaluating a relay according to second embodiment.
[0040] FIG. 9 shows a series of tables illustrating a second method
of evaluating a relay according to a second embodiment.
[0041] A mobile communications network comprises, in part, a base
station or access point 10 and a plurality of mobile handsets 20.
Each base station 10 controls communication within an area, called
a cell. FIG. 1 shows an example of a network architecture.
[0042] Communication is performed by sending radio wavelength
signals between the base station or access point 10 and a mobile
handset 20.
[0043] Base stations 20 are expensive and thus it is not practical
to build them in large numbers. Therefore relay devices 16 are used
to enhance coverage within the cell.
[0044] The relays 16 are extremely useful in areas with low base
station power, such as at the boundaries of the cell. They are also
useful to provide coverage in areas blocked by buildings (termed
`shadowed areas` in the art). It is known to fix relays to provide
coverage in `shadowed` spots. These relays are typically
repeaters--devices that amplify and forward on a signal.
[0045] Mobile relays may be provided in a network. Typically a
plurality of mobile relays will be used. The term `mobile` includes
the relays will be mobile with respect to their surroundings, as
well as the mobile terminals within the cell.
[0046] The mobile relays 16 may include user terminals, e.g. mobile
phones, PDAs and so on. Alternatively, the relays may be purpose
built hardware and mounted on buses, coaches and the like.
[0047] An aspect of the present invention comprises a relay
management function that quickly and efficiently controls which
relays 16 are used within a cell. The arrangements described below
relate broadly relate to two aspects of the invention. However, it
will be readily apparent that the concept is to allow the
adaptation of the network to evaluate and select the most
appropriate relays for use in the network.
First Embodiment
[0048] In a particular embodiment, each relay 16 is classified
according to a particular criteria. This may be its type, such as
fixed or mobile. If fixed, whether or not it is a high complexity
device, or if it is an repeater. If the relay is a mobile relay,
the classification may include what type of mobile; for example, it
may be classified as a mobile terminal, or a dedicated relay.
[0049] FIG. 2 shows a table that summarizes examples of the types
of relays available, and how they may be classified. Thus, as a
first classification they may be separated into two categories:
fixed and mobile. Sub-categories based on type and/or complexity
may then be made.
[0050] Each active relay communicates with a base station
controller 14 via a base transceiver station 12. Therefore, at any
given moment it will be known what active relays 16 are within a
particular area. By knowing the total amount of relays
communicating with the base station 20, and knowing which
classification each relay 16 is part of it is possible to know what
percentage of each type of relay 16 is within a given area. Using
the table of examples shown in FIG. 2, for fixed relays there may
be 70% high complexity relays and 30% repeater types.
[0051] As a large number of relays 16 are likely to be present
within a cell at any given time it is highly unlikely that each
relay will be required at any given moment. Thus it is desirable to
ensure that network resources are not wasted, or that interference
between signals is not induced by an overcrowding of signals.
[0052] When relays communicate with the base station 20, details of
their capabilities (e.g. peak power, data rate supported, power
constraint) are transmitted to the base station 20. Thus the base
station 20 can assess and compare the abilities of each of the
relays 16 within the cell. Alternatively the relays could each be
classified. Instead of each relay signalling its capabilities
(which may induce delay and require the implementation of
signalling requirements) it could transmit its class to the base
station. Therefore, instead of using (for example) 20 bits for
instructing a base station of its abilities, (for example) 5 bits
could be transmitted defining the class of the relay. This approach
demands that a classification of each type of relay is made in
advance.
[0053] The capabilities of each detected relay 16 is reassessed at
given intervals. This may be, for example, every 30 seconds. The
number of mobile terminals within the cell, and the usage
requirements are also monitored. As the usage requirements increase
or decrease, the number of relays used within the cell is
adapted.
[0054] The network may reassess the capabilities of the relays
based upon triggers, rather than periodically. The triggers may be
the registration or de-registration of a relay 16 with the base
station 20, or it may be upon a request to the network for more
resources. Alternatively a combination of periodicity and triggers
may be used.
[0055] On the basis of the capabilities of each of the relays, the
number and usage requirements of mobile terminals 14, the base
station 10 is operable to adapt the number of relays 16 used.
[0056] Specifically the base station 20 comprises means (in the
form of an algorithm) to assess the specific needs within the cell,
and select the optimum relays to meet the needs. The algorithm may
be located at either the base station controller 14 or at each base
transceiver station 12. Generally, if the algorithm is located at
the base station controller the algorithm can be used to control a
larger area--a single base station controller 14 will generally
control a plurality of base transceiver stations 12. Although, in
an alternative arrangement, if the function is located at the base
station controller 14 the algorithm may be configured to perform an
evaluation of relays 16 just in a single cell. If the algorithm is
located at the base transceiver station 12 the processing time is
much reduced as there is one less step in the process chain.
[0057] In a preferred arrangement a number of predefined scenarios
within the cell will be proposed. Each scenario will propose (at
least) usage requirements for a particular area, a particular
timescale and if any specific demands are needed. For example
scenario 1 may relate to a small area within the cell and that a
low bit rate is required, scenario 2 may relate to a large area and
that high power is required and so on. A particular scenario may be
a small area with high usage demands (for example to deal with the
aftermath of a concert or a football match).
[0058] For each scenario, the available relays of the cell are
evaluated and are rated based on the needs of the hypothetical
users in that scenario. Thus the appropriate number and type of
relay are predefined for each scenario. When in use, if the base
station assess that the usage requirements meets a particular
scenario (or most closely meets a particular scenario), the
appropriate relays have already been predefined, and hence can be
easily introduced to the network. The remaining relays can be
withdrawn from the network to save resources and ensure that
interference does nor occur. Thus, if the base station 10
ascertains that the usage demands are most similar to the demands
of hypothetical scenario 7, the relays redefined as being the
optimum solution for scenario 7 are introduced into the network,
and the remaining relays taken out of service.
[0059] When considering the capability of each of the relays at
least the following are taken into account: [0060] What data rate
is supported by the relay. [0061] Does the relay have any power
constraint. For example, if a mobile user terminal or a lap-top
user used, there is the possibility that the terminal may be turned
off. [0062] The peak power that the relay can transmit at. [0063]
Does the relay support layer 1 (e.g. power control coding schemes)
techniques. [0064] Are higher layer techniques supported. [0065]
What type of carrier is the relay mounted on. For a fixed relay
this will not be important. However, it is important for mobile
relays; it would be undesirable for the relay to leave the cell
whilst it was in use.
[0066] Additional factors need to be assessed when selecting the
appropriate relays for each scenario. These include estimating
whether selecting a particular number of relays will cause
interference with one another.
[0067] An assessment of the location of the relays is also made.
For example, if a plurality of mobile relays are each mounted on a
bus, then it is important to known where the buses will be. By
considering the bus routes and time-tables an estimation can be
made of the buses location at any particular time. From this
information, as well as road speed limits, an estimation as to the
speed of bus (and hence the relay) can be made.
[0068] Within each cell, for each scenario, specific dynamic and
static requirements are predetermined. Examples of types of
requirements are set out in table 1 below. TABLE-US-00001 TABLE 1
Dynamic Requirements Data rates requested (from users and/or
specific service - eg MBMS. Mobile terminal population and
dispersement. Power and coverage requirements Static Requirements
Coverage area, and characteristics of said area. Power
requirements. Velocity requirements.
[0069] In order to meet certain requirements in certain scenarios,
weighing factors may be attached to one or more of the above
requirements. For example, if a certain scenario requires specific
power requirements, only relays that are able to meet these
requirements are used.
[0070] All of the above parameters may be used to set up a list of
the required degrees of freedom that can be used by the evaluation
algorithm to evaluate each relay. Generally, a list of first, high
level objectives are defined, which are then elaborated into
further, lower level objectives/attributes. An example of this
arrangement is illustrated in FIG. 5.
[0071] In the present embodiment, all of the above objectives and
attributes are taken into account into a process which yields the
optimum relay or number of relays to cover specific needs. Two
possible outcomes of the selection process could be as follows:
[0072] The relays 16 evaluated are all ranked (for example with 10
relays, from 1 to 10). The best 4 are then selected to meet the
scenario requirements, the next best three are maintained in a
`ready` status, and the lowest three are discarded and not
used.
[0073] Alternatively, a number of optimum relays are selected for
each scenario. The relays are still ranked, but scenario 1 may call
for using the best 4, and having the next best 2 on standby.
Scenario 2 may call for using the best 3, and having the next 4 on
standby and so on.
[0074] A specific realisation of an embodiment of the present
invention will now be described, particularly demonstrating the
realisation of a possible evaluation algorithm.
[0075] FIG. 5 shows a diagram that defines high level objectives,
and, in a hierarchical manner, attributes associated with each
objective. The attributes may be used to evaluate the objectives.
For example, if a particular objective relates to `power`, then the
first level attributes of the relay may be its peak power, total
power availability and expected remaining functioning time at the
current power value. Each relay will have a value associated with
each of the attributes, and hence each of the available relays can
be assessed, and the `power` rating for each of the relays
evaluated.
[0076] Other objectives may be what layer techniques are supported,
or what level of transmission can be supported.
[0077] Table 2 set out below shows an example of three relays (R1,
R2 & R3), and characteristics of each relay as assessed based
on the hierarchical objective/attribute system described above.
TABLE-US-00002 TABLE 2 R1 R2 R3 objective A Layers attribute L1
techniques yes yes yes supported A1 supported attribute L2
techniques no yes yes A2 supported attribute L3 techniques no no no
A3 supported objective B Power attribute Peak power (W) 1 4 2 B1
attribute available time at 2 4 50 B2 current power (hrs) objective
C Other attribute Bit rates supported 3 6 9 C1 (Mbps) attribute
Velocity (km/h) 5 1 40 C2
[0078] In this example, R1 may be a PDA, R2 a laptop computer and
R3 a custom relay mounted onto a bus. The objectives are set out on
the left hand side of the table, and the attributes in the columns
on the right hand side. The numbers represent technical
characteristics associated with each objective. For example, and
relay that supports layer 1 techniques a `yes` value is assigned.
In this example, all relays support layer 1, no relay supports
layer 3 and R2 and R3 support layer 2.
[0079] Where it is possible, numeric values are used. For example,
when considering the velocity of the relay, the PDA (R1) is
travelling at 5 km/h, the laptop (R2) at 1 km/h and the bus-mounted
relay is travelling at 40 Km/h. For attributes such as velocity and
location, the base station may request that the relay provides
regular up-dates in order that the information relied upon is as
accurate as possible.
[0080] FIG. 6 shows a specific realisation of an evaluation
algorithm. Table 1 of FIG. 6 corresponds to table 2 above.
[0081] Table 1 shows a list of the high level objectives, and
specific attributes associated with each of the objectives.
[0082] Table 3 shows a weighting associated with each of the
attributes. The weighting factors will vary for each scenario, and
those shown in table 3 are only shown by way of an example. In any
event the sum of the weighting factors for each of the attributes
for each objective must total 1. In other words, the weighting for
each objective must equal 1.
[0083] Table 2 shows a combination of table 1 and table 3. The
attribute values in table 1 have been replaced by numeric values
representing the performance of each relay with respect to one
another. This may be achieved by a predetermined `look-up table`,
or by assessing individual relays and providing a basic formula
that can be applied.
[0084] Table 4 shows weighting factors for each objective (in this
case: power, layers supported and others). Again the sum of each of
the weighting factors must be one.
[0085] Table 5 shows the sums of the multiplications between
weighting factors and attributes of table 2--i.e. the values
associated with the attributes from table and the weighting factors
calculated and shown in table 3.
[0086] The results for each objective are then summed, as shown in
table 6. Thus the values for R1 in table 5 for the first, second
and third attributes (corresponding to the first objective) are 40,
18 and 15. Thus the numeric value shown in table 6 for the first
objective is 73. Table 6 also shows that the summed attributes for
each objective are subjected to a weighting factor (from table 4).
The results are shown in table 7. This table shows the
multiplication between attributes and weighting factors for each
objective for each of the objectives. Table 8 shows the combined
totals of each of the objectives, and hence provides a final
numeric total of how each of relays R1, R2 and R3 compare when
considering three particular objectives. Table 9 shows the final
ranking of the three example relays. It will be apparent that R3 is
ranked first, R2 is ranked second and that R3 is ranked third.
[0087] It is also envisaged that there will be scenarios when the
algorithm is bypassed, typically when very select criteria have to
be met. For example, when all of the relays that are to be used are
to be selected solely on the basis of their peak power attribute,
then only relays with the requisite peak power need to be
considered, and relays of this type are then compared. This is akin
to having weighting values of 1.0 for the required attribute and
0.0 for each of the other attributes.
[0088] FIG. 4 shows an embodiment of a signalling function. For
this example, it is assumed that the evaluation and management
algorithm is located at the base station controller, and that the
base station controller controls only one base transceiver
station.
[0089] Each of the relays register with the base station
controller, when they enter the cell, or are switched on. During
the registration process details of the capabilities of the relays
is transmitted.
[0090] Periodically the base station controller pages each of the
relays (including user terminals willing to act as mobile relays)
to requesting any updated information, or current status
information, for example power availability.
[0091] The relays transmit their location to the base station
controller. This process may be repeated as often as power and
processing constraints allow.
[0092] The base station controller also requests any further
information it may require from other sources--e.g. the core
network.
[0093] Once all information has been collated the base station
controller uses the evaluation algorithm to evaluate each of the
relays and form a ranking list of each of the relays for
objective.
[0094] When a new relay is activated, or enters or leaves the cell
the system performs a re-evaluation after paging each of the relays
for information.
[0095] The above embodiment takes particular use in a network
comprising one or more mobile relays. This is because mobile relays
form a dynamic environment, where the number, and characteristics,
of relays may alter.
Second Embodiment
[0096] In a further embodiment the evaluation of each of the relays
16 will occur at the relays. This arrangement avoids undesirable
additional signalling. This embodiment is particularly suitable for
a network comprising a plurality of mobile relays, where relays may
regularly leave and enter the cell.
[0097] In this arrangement a base station 10, or access point, will
evaluate usage demand by calculating its own usage demands, that of
terminals associated therewith, as well as previously active relays
16 (particularly mobile relays). From these calculations the base
station/access point 10 will define the needs of the cell. This may
be achieve by defining scenarios that relate to pre-set usage
requirements. As described in the first embodiment the relays may
take the form of dedicated mobile relays, such as a relay mounted
on a bus or train. However, they may take the form of a further
user device such as a mobile phone 20, or lap-top. These devices
generally already have an element of in-built relay functionality.
However, the drain on battery power is particular drawback.
[0098] The pre-set usage requirements are converted into numerical
values relating to specific parameters of the network. For example,
the values may relate to minimum power requirements for a
particular relay, or, in the case of a mobile relay, a particular
minimum or maximum speed of travel.
[0099] The base station/access point 10 then transmits the
information on a broadcast channel to each of the relays 16 in the
cell. Therefore, each relay needs to synchronise to this particular
channel. This arrangement can negate the need for relays to
register with the base station 10, and hence saves signalling
resources. However, in a preferred embodiment the relays each
register with the base station 10.
[0100] Once a relay 16 has received the information transmitted
from the base station or access point 10 the relay 16 will compare
its own capabilities with the requirements. This process is
described in more detail below.
[0101] The data transmitted to the relays from the base station 10
can be in the form of pre-set scenarios designed as models
configured to cope with predetermined usage requirements. By
comparing its own capabilities with the requirements for a
particular scenario each of the relays 16 can effectively decide if
they are suitable for use in conjunction with the current
scenario.
[0102] If a particular relay fits with the scenario requirements
the relay 16 may begin performing relaying functions. Alternatively
the relay may first register with the base station/access point 10,
and begin relaying functions once successful registration has
occurred. In a preferred arrangement the relay may periodically
compare its capabilities with the usage requirements to assess
whether or not it still meets usage requirements. This may be
because additional relays have entered the cell, or that the relay
characteristics (such as location) have changed.
[0103] If a particular relay 16 does not meet the scenario
requirements it may remain idle. Preferably the relay 16 will
remain idle until it receives a further signal from the base
station or access point 10. This signal may be, for example,
further scenario requirements, as the usage demands in the cell may
have changed. In an equally preferred arrangement the idle relay
may retry matching its capabilities to the scenarios requirements
at pre-set intervals. This may be advantageous if all of the relays
are mobile. For example, if at a first instance a particular relay
does not meet the requirements because there are other more
suitable relays, then it will remain idle. However, as the relays
are mobile they may move out of the cell. In this case the relay
may become one of the most suitable in the cell. A particular
arrangement where this suitable is if mobile handsets/PDAs/lap-tops
20 are being used as relays, and they are turned off by their
users. The network then needs to reconfigure the most appropriate
relays 16 for use in the network.
[0104] Some scenarios may be such that most relays 16 would be
suitable to meet the usage requirements. Therefore it is preferable
to ensure that all relays do not attempt to register with the base
station/access point 10 or begin relaying functions. This will
result in many unrequired signals being transmitted, and hence may
cause interference.
[0105] Therefore, to avoid all relays registering with the base
station, or beginning to function automatically, the base station
10 defines a limited number of relays 16 that are to function in
each scenario. This information is typically transmitted with the
usage requirements/scenario information.
[0106] In a preferred arrangement the base station or access point
10 may comprise a counter that counts the number of operational
relays within the cell. This arrangement preferably works in
conjunction with the relays 16 registering with the base station
10. Accordingly, once the required number of relays 16 is reached,
no further relays are permitted to be registered with the base
station in the cell, even if they fulfil the scenario requirements.
When the required number of relays has been reached the base
station transmits this information on the broad cast channel to all
of the relays. The relays that have not been accepted for use in
the network may then cease comparing their own capabilities with
the scenario requirements. However, they may periodically
re-compare their capabilities with scenario requirements, in case
requirements alter. Alternatively, or as well as, the relays not
accepted may further compare their capabilities based on external
triggers.
[0107] However, as usage demands change, the optimum scenario may
also change, and hence the base station or access point 10 may
re-broadcast to all of the relays the required capabilities for the
new scenario. Each relay 16 may then re-evaluate its capabilities
against the new requirements.
[0108] A example of an algorithm operable to allow only appropriate
relays to function to meet a specific scenario is described below
with reference to FIG. 7.
[0109] The base station or access point 10 gathers information
regarding the usage demands in the cell, and then sets criteria to
ensure that the most appropriate relays are used to meet the
demands. These criteria include specific values that are associated
with relay characteristics, such as transmission power, velocity
(for a mobile relay), area of coverage, and so on. Relay type is
also an important consideration. If mobile handsets 20 are used as
relays in the network there is the possibility that they may leave
the network, be turned off, or cease functioning when their battery
is drained.
[0110] The base station 10 broadcasts this information, together
with an upper limit on the number of relays required, on a channel
receivable by all of the relays 16 in the cell.
[0111] The relays, on receipt of the transmission, assess their
characteristics with those required to meet the usage demands. It
may be that the base station transmits specific requirements
relating to particular characteristics to each of the relays, and
if they do not match or better these values they are not considered
suitable for use in the network to meet the present usage
demands.
[0112] FIG. 8 shows a further example of how criteria of scenarios
are correlated with characteristics of specific relays. This
example relates to mobile relays--ie those relays that are mobile
with respect to the base station and the handsets within the cell.
It will be appreciated that the example shown illustrates a
simplified scenario to allow for easier illustration. In this
scenario (scenario 1) the two important characteristics are power
and velocity. In FIG. 8 it will be seen that specific values have
been associated with particular power ratings and particular
velocities. For example, a power rating of 0-1 watts is assigned
the rating of 20 (i.e. just a numerical value), whereas a velocity
of 20-60 km/h is assigned a value of 40. Using ratings in this
manner allows for a relay to calculate if it is suitable for use in
the system. There may be many criteria that need to be consider,
and it may be that not many relays satisfy all criteria. Therefore
it is necessary to consider a `best fit` for all relays. For
example it may be that a specific velocity, power and supported bit
rate are required. It may be acceptable if a relay has more than
sufficient rating for velocity and bit rate, but not sufficient
power.
[0113] Consider now a specific relay and particular usage demands
in the form of a pre-defined scenario. In the example the required
scenario values are shown in bold type-face. The values associated
with the relay are underlined. The scenario calls for a relay with
a power of 4 to 6 watts and a velocity of 5 to 20 km/h. It will be
seen from FIG. 8 that these values correspond to assigned values of
70 and 60 respectively. A combined value for the scenario is
therefore 130.
[0114] A specific relay has a power of 1.5 watts, and a velocity of
0.5 km/h. These characteristics correspond to values of 40 and 100
respectively. Thus a combined value for the relay is 140. In this
specific example the relay does not have sufficient power; 2 to 4
watts are required, whereas the relay has only 1.5 watts (i.e. 1 to
2 watts). Hence an assigned value to 70 was requested, whilst the
relay only has an assigned value of 40.
[0115] However, the relay exceeds the velocity requirements. In the
example scenario a velocity of 5 to 20 km/h is acceptable. However,
the relay has a speed of 0.5 km/h (i.e. 0-1 km/h), which is
considered to be superior. Accordingly the value assigned to the
relay's velocity rating is 100. Therefore the combined total for
both velocity and power is 140. This is higher than the network
required 130, and accordingly the relay is suitable for use in the
cell.
[0116] In scenarios where a particular criteria is essential then a
sub-optimum solution for this characteristic is not acceptable.
This information may be transmitted by the base station 10. For
example, a minimum power of 3 watts may be required. Even though
the present relay 16 is sufficient overall, it does not meet the
requirements of for power, and hence it is not suitable for use on
the network.
[0117] A further variation of the present embodiment is described
with reference with to FIG. 9. This arrangement allows for a
particular relay to ascertain which scenario it best fits. The
arrangement described in relation to FIG. 9 introduces the concept
of weighting factors. FIG. 9 comprises two tables, the first
relating to a first scenario and the second relating to a second
scenario.
[0118] Each scenario still uses both power and velocity. However,
weighting factors have been introduced into each of them. Broadly,
it will be seen that in scenario 1 the velocity requirement is more
important than the power requirement. The reverse is the case in
scenario two.
[0119] Values are assigned in a similar manner as in the
arrangement described with reference to FIG. 8. However, it will be
noted that in table 1, the power characteristic has been assigned a
weighting factor of 0.2, whereas the velocity characteristic has
been assigned a weighting factor of 0.6.
[0120] The values in bold typeface indicate the requirements needed
to meet a particular scenario. The values that are underlined
indicate the values that a particular example relay has. These
relay values are the same as for the previous arrangement.
[0121] In this arrangement the network is effectively classifying
the relays into user groups for each scenario. Accordingly the
weighting factors for each characteristic in all scenarios (e.g.
velocity, power and so on) must sum to 1. There are only two
scenarios in this example, but it will be appreciated that in
practice there may be many more scenarios. In the example given the
weighting factors associated with power are 0.2 and 0.8, i.e. a
total of 1. Therefore, when defining scenarios, the most important
characteristic can have the highest weighting.
[0122] From the tables in FIG. 9 it is apparent that the desired
value, (or minimum value) for scenario 1 is 50, whereas for
scenario 2 it is 80. The calculated value for the relay in each
case is 68 and 72 respectively. Thus, comparing the values for each
of the relays with the required value it will be seen that the
relay is more suitable for the first scenario. Even though the
calculated value of the relay is higher for the second scenario (72
instead of 68) it is more suitable for the first scenario because
its calculated value (i.e. 68) is higher than the required value
(i.e. 50). Whereas for the for the second scenario the relay is
rated at 2, but the requirements for the system are 80. Therefore
the relay is not suitable for the particular scenario.
[0123] Thus relays 16 will all have a rating value for each
scenario. Therefore it is possible to rank the relays numerically.
Accordingly, each scenario will have an associated list of suitable
relays. Thus, it may be that in a particular scenario eight relays
are required. The first eight relays on the list will be the
optimum relays to meet the needs of the scenario. However, it may
be that a number of scenarios are being run in the cell at any one
time. Therefore, if a particular relay is not available for a
scenario, because it is active within a further scenario, the next
most suitable relay can be introduced in to the new scenario. In
this embodiment the base station may continue to broadcast to all
relays that a particular pre-defined scenario is required to meet
current usage demands. The base station 10 continues to broadcast
until the most optimum relays available register with the base
station 10. As a hierarchical list of each of the relays 16 has
been ascertained for each scenario, the relays with the highest
rating for that scenario attempt to register with the base station.
After a pre-determined time delays the next most optimum relays
attempt to register. Thus if two relays 16 that would be the most
optimum in a particular scenario do not register, after a
predetermined time the next two most optimum relays attempt to
register.
[0124] This arrangement negates the need for communication between
the individual relays, and hence avoids additional signalling and
processing in the network.
[0125] The base station/access point 10 may periodically broadcast
new information, such as a change of scenario to meet new usage
demands, or when mobile relays 16 leave or enter the cell. These
factors may change the relay values, and particularly effect the
position of relay on the numerical list. Accordingly the relays in
use during a scenario may change within the duration of the
scenario as more appropriate relays enter the cell, or particular
relays leave the cell.
[0126] In an alternative embodiment the Relays may each assess
themselves against a particular scenario. In this case the
weighting factors for each characteristic in a particular scenario
(e.g. velocity, power, bit rate supported) must sum to 1. However,
this arrangement is less desirable because it is difficult for each
of the relays to compare their abilities with the other relays.
Therefore information must be transmitted to the base station 10
for processing. Accordingly further signalling and processing is
required. In embodiment 1 above the processing was performed by the
base station controller 14, base transceiver station 12 or access
point 10, with no, or little, processing performed at the relay 16.
In this embodiment it is desirable that the processing is performed
by the relays. However, this arrangement results in processing
being required at both the base station and the relay.
[0127] In a preferred arrangement the algorithm may also be based
on the location of the relay. This is particularly important for
mobile relays. Certain scenarios may be location orientated, for
example due to an large gathering at a particular place, such as at
a football match, or in rush hour. In this case the required
location is transmitted by the base station or access point, and
the relay first calculates its position (for example using
triangulation techniques) to see if it fits with the scenario
requirements.
[0128] It is to be understood that the above describes embodiments
are set out by way of example only, and that many variations or
modifications are possible within the scope of the appended
claims.
* * * * *